MPs have rejected attempts to cut the upper time limit for abortions.
A series of amendment to the Human Fertilisation and Embryology Bill had called for the upper 24-week limit to be reduced to between 12 and 22 weeks.
But an amendment calling for a 20 week limit was defeated by 332 to 190 votes on Tuesday.
MPs also voted to remove the need for clinics to consider a child's "need for a father" when offering fertility treatment, increasing parental rights for lesbians and single women.
Conservative Iain Duncan Smith's amendment to tighten the law on IVF treatment was defeated by 292 to 217 votes.
Gordon Brown had allowed MPs to vote with their consciences on the measure following concerns over a backbench rebellion from a number of Catholic MPs.
Supporters say the move would increase equality for lesbian couples and single women, but critics have warned that it undermines a child's need for a father.
Speaking during the debate, Duncan Smith called on MPs to "examine their consciences" and protect the status quo.
"We want people to recognise that fathers have a major role to play and if they're not around then let's find a way of making sure that their influence can still be found," he said.
Tuesday's debate came after MPs backed the use of animal-human hybrid embryos for medical research by 176 to 336 votes on Monday.
An attempt to ban so-called 'saviour siblings' – selected by parents to provide tissue material to help a sick child – was also defeated by 342 votes to 163.
Conservative MP Nadine Dorries, who tabled the amendment calling for a 20-week limit, told ePolitix.com: "The way abortion takes place post-19 weeks is very different to the way abortion takes place pre-19 weeks.
"We're talking foeticide – surgically dismembering a baby, removing it limb by limb, giving it a lethal injection to the heart first – and I just think in a civilised society that's not a way to behave.
"Also, we know that babies born earlier than that could live if they receive the right treatment and attention and we know also babies feel pain in the womb down to 18 weeks.
"So on the issue of pain and viability there's a very strong case that it's now time to reduce to 20 weeks."
And Tory leader David Cameron said he would "certainly" be voting for a 22-week limit.
"I think this is a really difficult issue, it is another issue of conscience, there is no party whip, Conservatives will be voting in all sorts of different directions," he told GMTV.
"I think the reason personally why I want to see it come from 24, definitely to 22, is because there are now children surviving, being born at 22, or 23 weeks.
"I think that it is very difficult to have a system that is aborting foetuses at that age when children are surviving. That is my personal view."
However, Brown believes the limit should remain at 24 weeks and some 86 MPs have signed a cross-party Commons motion describing the current limit as "scientifically and ethically justified".
Ministers have also warned that suggesting babies born before 24 weeks could survive gives false hopes to the parents of premature infants.
And health minister Dawn Primarolo said there had been no improvement in survival rates since the current limit was set in 1990.
Stressing the importance of protecting women's right to choose, she also insisted there was no evidence requiring the abortion laws to be changed.
"There is no science that shows us that the survival rates have changed since we took the decision to have the time limit at 24 weeks," Primarolo told BBC Two's Newsnight.
"That is supported by the BMA [British Medical Association] and the Royal College of Obstetricians."
21 May 2008